Device for regulating constant-current dynamo-electric machines



.(No Model.)

0. OFFRELL.

DEVICE FOR REGULATING CONSTANT CURRENT DYNAMK ELEGTRIG MACHINES.

T T jatented Jul 18, 1893.

JNITED it nrnsrr Geri-on,

OLOF OFFRELL, OF MlDDLETOlVN, CONNECTICUT, ASSIGNOR TO THE SGI-IUYLERELECTRIC COMPANY, OF CONNECTICUT.

DEVICE FOR REGULATlNG CONSTANT-CURRENT DYNAMO-ELECTRIC MACHINES.

SPECIFICATION forming part of Letters Patent No. 501,582, dated July 18,1893.

Application filed December 12, 1892. EiBl'ltLl No. L54,899. (N0 model.)

To all? whom it may concern:

Be it known that I, OLOF OFFRELL, a citizen of the United States,residing at hliddletown, in the county of Middlesex and State ofConnecticut, have invented certain new and useful Improvements inDevices for Regulating Constant-OurrentDynamo-ElectricMachines; and I dohereby declare the following to be a full, clear, and exact descriptionof theinvention, such as will enable others skilled in the art to whichit appertains to make and use the same, reference being had to theaccompanying drawings, and to the letters of reference marked thereon,which form a part of this specification.

Myinvention relates todynanio electric ma chines, audits objects are toprevent waste of power, and enable the speed of the motor to beaccurately and, if desired, automatically regulated.

The speed of a series motor c epends upon the electromotive force of thecurrent and the resistance of the circuit. Nhen the current and theresistance of the circuit remain constant, the speed can be controlledonly by va rying the strength of the field, that is, the number of linesof force passing through the arinature. This is usually done byswitching in or out coils of the field magnet; but it has been proposedto use a magnetic shunt, to divert some of the lines of force from theirnormal path through the armature. My deflector is such a device, beingbased upon the fact that 'the lines of forcein a magnetic field tend tofollow the path of least magnetic resistance, and the invention consistsin a movable iron shunt, or deflector, arranged between the mature andthe pole pieces. "he lines of force follow the deflector when it ismoved on;- of line With the armature and pole pieces, thereby decreasingthe number of lines passing through the armature and weakening thecounter-electromotive force. When the deflector is moved back into linewith the pole pieces, more lines of force pass through the armature.

In the drawings,-Figure 1 is an elevation of a motor embodying myinvention. Fig. 2 shows the deflector in perspective; and Fig.

3 is a diagram of an automatic regulator.

Between the armature A and the faces the pole pieces l; of the fieldmagnet, are interposed two plates 0 of iron, preferably wrought iron.The plates are segments of a cylinder whose axis coincides with that ofthe armature shaft. They each include about a quarter 01" the circle,and are carried on arms d projecting from a sleeve D, which is free toturn on the armature shaft a, or other suitable bearing concentrictherewith. The plates extend preferably from one end of the armature tothe other.

The operation of my invention is as follows: When the load on the motoris decreased, the armature tends to increase in speed, or race. Thisdevelops an increased counter-electromotive force, tending to cut downthe current. in order to keep the current constant, thiscounter-electromotive force must be reduced, and this can beaccomplished by weakening the field, that is, the number of lines offorce out by the armature coils. My invention effects this by enablingthe operator to deflect some of thelines of force awayfrom the armature,by turning the deflector so as to move the plates C partially or whollyout from between the pole pieces and the armature: since the lines offorce seek the path of least magnetic reluctance, an d will follow theplates out around the armature. The result is the same as though thecurrent flowing through the coils of the field magnets had beenweakened. The armature coils cut fewer lines of force, and thus thecounter-electro motive force is dimin ished. By varying the position ofthe deilector to correspond with the changes in load, a regular speedmay be maintained.

The deflector may be moved by hand, suitable locking devices being usedto hold it when adjusted. I prefer, however, to render it antomatic inits action, in order to keep the motor at a constant speed undervariations in the load. To this end, an arrangement such as is shown inFig. 3 may be used. An arm d projects from the sleeve D, carrying asegment gear (Z with which meshes a segment gec on the end o'f'a leverE, the other end of which is attached to the movable ooreFof a solenoidH. A spring I keeps the lever norma iy against a stop It, in whichposition the deflector lies between the pole pieces and the The solenoidis in shunt from the Ftilidtt rure.

brushes L L of the motor armature A,b being the field magnet coil. Thesolenoid is responsive to the eounter-electromotive force generated bythe armature, and when this increases upon a decreasing of the load, thesolenoid attracts its core, thereby moving the lever and swinging thedeflector outof line with the pole pieces, in order to weaken the fieldand reduce the counter-electromotive force, as above set forth.Thetension of the spring may be adjusted to render the regulating actionof the solenoid automatic within given limits.

The effect due to the shunting of the magnetic lines is augmented by theincreased width and consequent greater magnetic resistance of theair-gap between the armature and the pole pieces, when the plates areswung out from between them.

I have described the regulator as applied to a motor but it is equallywell applicable to a dynamo.

Having thus described my invention, what I claim is 1. A regulator for adynamo electric machine, consisting of an iron plate adapted to be movedbetween the armature and the pole of the field magnet, substantially asdescribed.

2. A regulator for a dynamo electric ma chine, consisting of an ironplate adapted to be moved from one pole of the field magnet toward theother pole, substantially as described.

3. A regulator for a dynamo electric machine, consisting of an ironplate lying between the armature and one pole of the field magnet, andadapted to be moved out toward the other pole, substantially asdescribed.

4. A regulator for a dynamo electric machine, consisting of a curvediron plate parallel with the armature, and mounted to move eoncentrically therewith, substantially as described.

5. A regulator for a dynamo electric machine, consisting of two curvediron cylindrical quadrants mounted to move concentrically with thearmature, substantially as described.

6. An automatic regulator for a dynamo electric machine, comprising amovable magnetic shunt around the armature, and a solenoid adapted tomove said shunt and responsive to changes in the counter-electromotiveforce of the armature, substantially as described.

7. An automatic regulator for a dynamo electric machine, comprising acurved iron plate lying between the armature and a pole of the fieldmagnet, and a solenoid connected in shunt around the armature andadapted to move said plate, substantially as described.

8. The combination with a dynamo electric machine, of curved platesmounted concentric with the armature shaft and between the armature andthe pole pieces, segment gears for operating said plates, a solenoidhaving a core attached to one of said gears and a spring for retractingsaid core, said solenoid being in shunt around the armature,substantially as described.

In testimony whereof I atfix my signature in presence of two witnesses.

OLOF OFFRELL.

\Vitnesses:

ERNsr LUNDGREN, W. J. MORGAN.

